PRIORITY

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63/063,794, titled METHODS AND COMPOSITIONS OF COATINGS FOR LED LIGHT BULB FILAMENTS, filed August 10, 2020, which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The present disclosure is generally directed to electric lighting, particularly light bulbs that employ light emitting diodes (LED).

BACKGROUND

[0003] Recent trends in the LED lighting field have pushed light bulb designs to expose the diodes as an elongated “filament” within the bulb envelope, which creates a vintage look that is currently popular with consumers. It is also well known to construct LED light bulbs that emit “white” light by combining a high-powered diode that emits blue light with a phosphor that emits yellow light via a Stokes shift of some of the blue light emitted by the diode. Because blue light and yellow light are complementary, they are together perceived as white light. By combining the above two technical advances, light bulbs have been constructed that mimic the look of traditional or vintage incandescent light bulbs when energized with an electric field.

[0004] Although such conventional designs are convincing when energized, the filament appears light yellow, yellow, dark yellow, or even reddish in color when unenergized (powered off) due to the necessary phosphor coating over the filament. Specifically, naturally present blue light interacts with the phosphor to emit the same yellow light, and so the filament itself looks unattractive if the light is unenergized.

[0005] It would instead be desirable for an LED filament to appear white in color, even when unenergized. It could be possible to put a coating over the filament to counteract this yellowish color. However, many coatings known in the art interfere with the light color produced by the diodes on the filament. Further, placing a coating on the envelope of the light bulb itself to counteract the yellowish color of the LED filament would also be undesirable because it would likewise interfere with the desired exposed appearance of the LED filament. Accordingly, there is a need in the art for a coating for an LED filament that does not dramatically shift the color spectrum produced by the LED filament and which also causes the filament to appear white or another similar color when the LED filament is unenergized.

SUMMARY

[0006] In one general aspect, the present disclosure is directed to an LED light bulb comprising: an LED filament; and a coating disposed in association with the LED filament, the coating comprising a composition comprising a binder and TiCh, wherein the coating is configured to not substantially shift a color spectrum produced by the LED filament and cause the LED filament to appear white when the LED filament is unenergized.

[0007] In another general aspect, the present disclosure is directed to an LED filament for a light bulb, the LED filament comprising a coating disposed in association with the LED filament, the coating comprising a composition comprising a binder and TiCh, wherein the coating is configured to not substantially shift a color spectrum produced by the LED filament and cause the LED filament to appear white when the LED filament is unenergized. [0008] In yet another general aspect, the present disclosure is directed to a method of making an LED filament, the method comprising: forming a slurry of a binder and TiCh; applying a phosphor coating to the LED filament; and applying the slurry to the LED filament over the phosphor coating, wherein the slurry forms a coating on the LED filament, the coating configured to not substantially shift a color spectrum produced by the LED filament and cause the LED filament to appear white when the LED filament is unenergized.

[0009] In various aspects, applying the slurry can be performed by one or more of dip coating, curtain coating, spray coating, or brush coating.

[0010] In various aspects, the binder and TiCh can be present in a ratio of about 1 :0.006 by weight.

[0011] In various aspects, the binder and TiCh can be present in a ratio selected from the group consisting of about 1:0.001, 1:0.005, 1:0.01, 1:0.05, 1:0.1, or 1:0.5 by weight.

[0012] In various aspects, the binder can comprise silicone.

[0013] In various aspects, the coating can be configured to substantially cover the LED filament.

FIGURES

[0014] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the invention and together with the written description serve to explain the principles, characteristics, and features of the invention. In the drawings:

[0015] FIG. 1 depicts various embodiments of LED light bulbs having a coating on the filaments configured to appear white when unlit in accordance with some embodiments. [0016] FIG. 2 depicts another embodiment of an LED light bulb having a coating on the filaments configured to appear white when unlit in accordance with some embodiments.

[0017] FIG. 3 depicts another embodiment of an LED light bulb having a coating on the filaments configured to appear white when unlit in accordance with some embodiments.

[0018] FIG. 4 depicts another embodiment of an LED light bulb having a coating on the filaments configured to appear white when unlit in accordance with some embodiments.

[0019] FIG. 5 depicts another embodiment of an LED light bulb having a coating on the filaments configured to appear white when unlit in accordance with some embodiments.

[0020] FIG. 6 depicts another embodiment of an LED light bulb having a coating on the filaments configured to appear white when unlit in accordance with some embodiments.

[0021] FIG. 7 depicts another embodiment of an LED light bulb having a coating on the filaments configured to appear white when unlit in accordance with some embodiments.

[0022] FIG. 8 depicts a conventional LED light bulb that appears yellow when unenergized.

DESCRIPTION

[0023] This disclosure is not limited to the particular systems, devices and methods described, as these may vary. The terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope.

[0024] As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Nothing in this disclosure is to be construed as an admission that the embodiments described in this disclosure are not entitled to antedate such disclosure by virtue of prior invention. As used in this document, the term “comprising” means “including, but not limited to.”

[0025] As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used.

[0026] As described above, there is a need in the art for a coating for an LED filament that does not substantially shift the color spectrum produced by the LED filament and causes the filament to appear white or another similar color when the LED filament us unenergized, counteracting the yellowish color of the LED filament while still preserving the desired aesthetics of the LED light bulb. Various illustrative coatings and their associated methods are described herein. Because of unique characteristics of the coatings described herein, various additional structural and functional modifications (e.g., characteristics of the LED driver circuit) correspondingly need to be made to allow the LED light bulbs with the filament coatings described herein to produce light with the appropriate color temperature (CCT) and flux, measured in lumens.

[0027] Referring now to FIGS. 1-7, various embodiments of an LED light bulb 100 are illustrated therein. The light bulb 100 can include one or more LED filaments 102 encased within an envelope 104 (also referred to as an enclosure or a bulb). The envelope 104 can be filled with an inert gas (e.g., argon, nitrogen, krypton, xenon, or helium) to conduct heat and, thus, cool the LED filament 102, as is known in the art. The LED filaments 102 can include multiple series- connected or parallel-connected LEDs disposed on a substrate. The substrate can be transparent. The LED filaments 102 can further include a yellow phosphor coating that converts the blue light generated by the LEDs positioned along the LED filament 102 into light approximating white light of the desired color temperature (e.g., 2700 K to match the warm white of an incandescent bulb or 5,000 K to approximate sunlight).

[0028] As noted above, the phosphor coating on the LED filaments 102 appears yellow in color when the filaments 102 are unlit. Accordingly, the filaments 102 can further include a coating disposed thereover that is configured to cause the filaments 102 to appear white when the filaments 102 are unlit or unenergized, rather than the conventional yellow as is shown in FIG. 8. In one embodiment, the coating can include a composition comprising silicone and TiCh present in a ratio of about 1:0.006, measured by weight. The composition can comprise a slurry comprising TiCh powder and silicone binder. This composition appears white under normal conditions and does not interfere with the color spectrum produced by the LED filaments 102. Accordingly, the LED filaments 102 appear white when unlit or unenergized and produce their normal, unaltered color spectrum when lit or energized. In other embodiments, the composition can comprise silicone and TiCh present in a ratio of about 1:0.001, 1:0.005, 1 :0.01, 1:0.05, 1:0.1, 1:0.5, or any ratio between any of the listed ratios, again measured by weight. The TiCh can be in one or more of the rutile (tetragonal), anatase (tetragonal), brookite (orthorhombic), or monoclininc phases. In other embodiments, the coating can comprise other materials. For example, the composition can comprise calcium-based materials in addition to, or in lieu of, TiCh. As another example, the composition can comprise other binders in addition to, or in lieu of, silicone. In various embodiments, the coating can substantially, entirely, or partially cover the LED filaments 102.

[0029] The coating and the filament can be produced using a variety of different manufacturing techniques and is not particularly limited. In one embodiment, the LED filaments 102 can be manufactured by forming a slurry of the silicone and the TiCh present in any of the ratios described above, applying a phosphor coating to the LED filament, and applying the slurry to the LED filament over the phosphor coating, such as by dipping the phosphor-coated filament into the aforementioned slurry. Additional production techniques include one or more of curtain coating, spray coating or brush coating.

[0030] The shape of the filament includes one or more of a straight rod, a spiral shape, a wave shape, a circular shape, an arch shape, a regular shape, a helix shape, or an irregular shape. The filament is constructed from a substrate that one or more diodes, phosphors, and coatings disposed on the substrate.

[0031] While various illustrative embodiments incorporating the principles of the present teachings have been disclosed, the present teachings are not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the present teachings and use its general principles. Further, this application is intended to cover such departures from the present disclosure that are within known or customary practice in the art to which these teachings pertain.

[0032] In the above detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the present disclosure are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that various features of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. [0033] The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various features. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0034] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

[0035] It will be understood by those within the art that, in general, terms used herein are generally intended as “open” terms (for example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” et cetera). While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of’ or “consist of’ the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups.

[0036] In addition, even if a specific number is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (for example, the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, et cetera). In those instances where a convention analogous to “at least one of

A, B, or C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A,

B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, et cetera). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, sample embodiments, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

[0037] In addition, where features of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0038] As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, et cetera. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, et cetera. As will also be understood by one skilled in the art all language such as “up to,” “at least,” and the like include the number recited and refer to ranges that can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1 -3 components refers to groups having 1, 2, or 3 components. Similarly, a group having 1-5 components refers to groups having 1, 2, 3, 4, or 5 components, and so forth.

[0039] Various of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.